The present invention relates to fission chamber radiation detectors, and more particularly to miniature small diameter detectors which are intended for in-core nuclear reactor use.
Such fission chambers are well known in the art, and in general a small amount of fissionable material is disposed within a gas-filled hermetically sealed chamber, with spaced-apart electrodes sensing current flowing through the gas as a function of incident radiation, as from a nuclear reactor core. The detector is typically electrically connected to a mineral insulated coaxial signal cable which brings the sensed signal current to remotely disposed electronic monitoring circuitry.
Since the detector is intended for in-core use it must reliably withstand this hostile environment. The sensitivity of the detector should be constant and the detector reliable in the high temperature hostile in-core environment. The most common source of detector failure is the failure of the ceramic to metal seal at the detector chamber to cable termination or end seal. It is desirable to provide a reliable cable end seal for such detector chambers.
A variety of prior art cable end seal structures utilize a ceramic end seal assembly to make a hermetic seal to mineral insulated signal cable, as seen in U.S. Pat. Nos. 4,139,724 and 4,137,423.